1. Field of Invention
This invention relates generally to plastic pallets, and particularly to plastic pallets especially suitable for stacking and for holding palletized barrels and drums by reason of special load-bearing surface configuration.
2. Prior Art
Pallets now in general use are not ordinarily specifically devised to hold drums or barrels, but rather are intended for use to store or transport numerous objects. Drums or barrels when stored or transported on pallets are susceptible to numerous problems. They are inherently unstable on a pallet subjected to varying motions and may slide, or tip and roll off the pallet. Wood pallets are unsuitable because they rapidly deteriorate when acid, oil or other solvents which are normally contained in drums or barrels, spill upon the wood pallet, and they may thereby rapidly deteriorate. In addition, the end boards of wood pallets are particularly susceptible to deterioration, and in use, they may become loose and rip off. Under such circumstances, the barrels or drums stored thereon may tip, and roll off of the pallet and their contents may thereby be spilled and cause very great damage.
Further, wood pallets are normally made in sizes which are not particularly suitable for containing barrels or drums, but are usually in such a size which gives them a certain degree of universality, but not special adaptability. It is recognized that pallets particularly devised for the ordinary or normal drum or barrel should be approximately 48".times.48" so that four drums or barrels may be placed thereon without any part of any barrel or drum extending outside the pallet periphery.
If resort is had to plastic pallets, one achieves the desirable attribute of resistance to spills of acids, oils, solvents and other liquid materials ordinarily contained in drums or barrels. But here again, the plastic pallets are not provided in sizes especially adapted for holding or transporting drums and barrels. Having solved the problem of resistance to deterioration by reason of spills, there still remains the problem of constructing such a pallet in the proper size, 48".times.48", which will be strong and stable and will not be deformed in carrying heavy loads so that the drums and barrels will roll off the pallet and cause great damage. It is noted that strength, stability, freedom from distortion under heavy loads is especially important since drums and barrels usually have capacity of 55 U.S. gallons, and water weighs 81/2 pounds per gallon, and oil may weigh approximately 71/2 pounds per gallon. It is therefor recognized that barrels or drums containing fluid or solid materials ordinarily weigh in the neighborhood of 400 to 800 pounds so that a suitable pallet especially devised for storing and transporting barrels and drums must be of great strength, free from the possibility of deforming under load so that tipping of barrels and drums and spilling of contents will not occur. In the use of a plastic pallet particularly devised for the storage of drums or barrels, there is a necessity for a fork lift operator to precisely position the tines of the fork lift so as to be symmetrical with respect to the center of gravity of drums stored on the pallet. Thus, a desirable attribute of a pallet specifically devised for storing and transporting barrels and drums would be a fork entry opening that is so limited in size and position that each blade of a lift truck can only enter under the pallet vertically below the center of gravity of the individual drum loads i.e. the drum centers, or slightly outboard of the drum centers. With such a desirable construction, stability can be achieved. Plastic pallets should have sufficient strength and stability so that drums can be stacked three high. In addition the pallets must be nestable, so that storage space and transportation space required for returning unloaded pallets may be utilized efficiently.